The present invention relates to a travelling vehicle system, and in particular, to prevention of a delay in control and system down which may occur when the overall length of a traveling path for travelling vehicles is increased to obtain a larger-scale system.
In a travelling vehicle system such as a tracking cart system, a running path is divided into a plurality of zones and a zone controller is provided for each zone so as to control a travelling vehicle that has entered that zone. A system controller is also provided for controlling these zone controllers, and a network is used to connect all of these controllers together. The system controller receives a conveyance instruction from an upper controller such as a distribution computer for the entire factory to correspondingly control the zone controllers, and report the results of conveyance to the distribution computer.
When the scale of the travelling vehicle system is increased and the running path for travelling vehicles is extended, a larger number of zone controllers are required and a delay may occur in the communication between the system controller and the zone controllers, thereby wastefully stopping travelling vehicles. Additionally, as the number of zone controller is increased, the limit of the capacity of the system controller is reached soon. When additional system controllers are then installed and assigned with different running paths obtained by dividing the original running path, if any of the system controllers becomes defective, the travelling vehicle system is shut down.
It is a basic object of the present invention to prevent, despite an extended running path, a delay in the communication between zone controllers and a system controller as well as the system-down of a travelling vehicle system.
It is an additional object of the present invention to enable the communication between adjacent group zone controllers without using any system controller in order to prevent a delay in control.
It is an additional object of the present invention to reduce communication burdens on an upper controller such as a distribution computer.
The present invention provides a travelling vehicle system comprising a running path for travelling vehicles which is divided into a plurality of zones and a plurality of zone controllers for controlling the travelling vehicles in the corresponding zones, the system being characterized in that the plurality of zone controllers are divided into a plurality of groups, a plurality of group controllers are provided for controlling the corresponding groups, and each of the group controllers backs up at least one of the other group controllers.
Preferably, communication lines are provided to connect the groups together without using the group controllers.
Preferably, one of the group controllers acts as a main controller so that an upper controller and the plurality of group controllers communicate with one another via the main controller, and at least one of the other group controllers is configured to back up the main controller.
According to the present invention, even if the running path for travelling vehicles is extended and the number of zone controllers is increased, since the zone controllers are divided into the plurality of groups, which are assigned to the different group controllers, the amount of time required for the communication between the zone controllers and the group controllers can be reduced to prevent a delay in control caused by a delay in communication.
Furthermore, in the present invention, the plurality of group controllers back up one another, so that the system-down of the travelling vehicle system can be prevented even if any of the group controllers is shut down. Thus, in a factory, if a travelling vehicle system is used for a basic conveyance system or the like which is used for inter-process conveyance, a larger-scale reliable travelling vehicle system is obtained.
Furthermore, the communication lines are provided to connect the groups together without using the group controllers. This communication lines are auxiliary and different from lines for connecting the zone controllers and the group controllers together. Thus, the entry of a travelling vehicle into the adjacent group or the like can be processed through the communication between the zone controllers without using the group controllers, thereby preventing a decrease in the speed of the communication between the zone controllers which may occur at the boundary between the groups.
Moreover, one of the group controllers acts as the main controller to allow the group controllers and the upper controller to communicate with one another. Thus, the upper controller needs to communicate only with the main controller as in the prior art. Additionally, since one of the group controllers backs up the main controller, the travelling vehicle system is not shut down even if the main controller is shut down.